1. Field of the Invention
The present invention is related to devices for cleaning storage tanks. In particular, the present invention is related to devices for removing oil and other sludge that accumulates in crude oil storage or process tanks.
2. Description of the Related Art
The accumulation of sludge in crude oil storage tanks and other liquid storage tanks is a problem faced by many companies and municipalities around the world that store crude oil before it is refined. Oil storage tanks must be cleaned periodically by manned crews usually shoveling out the sludge which accumulates on the bottom of the tank.
Cleaning oil or other liquid storage tanks is presently an arduous and hazardous task. As many as 15 or 20 people may be placed inside a tank to clean the sludge from the tank by hand and prepare the tank with hand tools for inspection or repair.
Placing workmen in a storage tank is very dangerous due to the flammability and volatility of oil and other liquids commonly stored in large tanks. Workers commonly must wear self-contained breathing equipment because the fumes from the chemicals stored in the tanks would suffocate or be toxic to the worker.
Commonly the access ports in the great majority of storage tanks are circular hatches or manholes which are commonly 24 inches in diameter. The size of the access port limits the size of any equipment used by the worker in cleaning the interior of a tank.
The following patents disclose art related to the present invention:
U.S. Pat. No. 4,770,711 discloses a method for cleaning chemical sludge deposits of oil storage tanks with a fluidizing agent, the tank having a floor, a side wall and a passageway through the side wall positioned adjacent the floor of the tank comprises a frame having a central portion and first and second end portions. The frame is configured and dimensioned to pass through the passageway. A pair of independently movable endless chain belts are position on opposite sides of the frame for selectively moving the frame within the oil storage tank to selected locations. A hydraulic line coupled to the central portion of the frame discharges the fluidizing agent onto an adjacent first portion of the sludge deposit so as to form a pool of sludge and fluidizing agent. A suction pump is positioned on the central portion of the frame for drawing up the poll of sludge and fluidizing agent. A suction pump is positioned on the central portion of the frame for drawing up the pool of sludge and fluidizing agent. A plurality of nozzles disposed adjacent the first end portion of the frame are in fluid communication with the suction pump so as to provide pressurized agitation and discharging of the pool of sludge and fluidizing agent onto a second portion of the sludge deposit adjacent said first end portion of the frame so as to dislodge and also aid in liquefying the second portion of the sludge deposit. The chain belts and suction pump are driven preferably by a pair of separately operable hydraulic motors supported on the frame.
U.S. Pat. No. 4,685,974 discloses a method for clearing settled sludge from the bottom of a storage tank uses a machine including a central body rotatable about which is a casing provided with two substantially diametric nozzles arranged so that liquid emerging therefrom sweeps substantially only in one plane, a turbine rotating the casing about the central body and half cylinder ensuring that when the casing is continuously rotated, alternately the nozzle is closed for substantially 180.degree. rotation while the other nozzle is open. Such machines may be suspended above the floor of the tank adjacent to a wall thereof. Liquid is emitted from the nozzles in a sweep substantially parallel to the bottom plane of the storage tank, thereby re-suspending the sludge which thereafter is withdrawn as a suspension.
U.S. Pat. No. 4,469,143 discloses a tank truck purging system to permit access for repair, or maintenance without environmental pollution or hazard to workmen entering the tank. In accordance with the invention an elongated cylindrical storage tank is tilted about its horizontal axis, to form a reservoir for purge water. The tank is connectable as by flexible hoses to fill and drain connections for a tank compartment of a truck, rail car, or other bulk liquid vehicle. Purge water is pumped from the storage tank at a level above the lower tilted end of the elongated tank and vapor displaced from the tank compartment by the water is recovered through a vapor recovery system. Desirably, the compartment is filed until it overflows into the vapor recovery line. Water is returned to the storage tank at a position near the upwardly tilted end. The tilted arrangement permits gravity separation and accumulation of minor amounts of light hydrocarbons, such as diesel fuel or gasoline at an upper separation zone formed by the upwardly tilted end. A similar separation zone or volume for accumulation of rust particles, sludge and the like is formed at the lower tilted end. Hydrocarbons lighter than water are flushed from the tilted upper end of the reservoir tank by adding water to the reservoir tank so that it overflows through a line connected to a separator tank. Heavy particles from the lower tilted end are removed through a cleanout line entering near the lower tilted end are removed through a cleanout line entering near the lower tilted end of the reservoir tank. Water may also be removed from the tank to lower the water level at the upper tilted end to increase the surface area of the separation zone for accumulation of such lighter hydrocarbons.
U.S. Pat. No. 4,407,678 discloses a sludge removal machine suitable for removing sludge from the bottom of a storage tank which comprises a central body rotatable about which is a casing provided with two substantially diametric nozzles arranged so that liquid emerging therefrom sweeps substantially only in one plane, a turbine rotation the casing about the central body and means ensuring that when the casing is continuously rotated, alternately one nozzle is closed for substantially 180.degree. rotation while the other nozzle is open. Such machines may be suspended above the floor of the tank adjacent to a wall thereof.
U.S. Pat. No. 4,223,622 discloses a tanker desludging system in a marine vessel adapted to carry liquids such as crude oil which embodies a certain amount of solid residue, apparatus is provided for removing the latter from the vessel's storage tanks. The liquid crude is normally removed by a manifolded discharge conduits, each conduit being fixedly positioned with its inlet port spaced above the floor of the tank to withdraw liquid from the tank. A portable cleaning apparatus is provided to remove accumulated sludge and the like from the tank floor, which cleaning apparatus is adapted to engage a discharge conduit whereby to ingest sludge from the latter.
U.S. Pat. No. 4,162,680 discloses a non-polluting system for metal surface treatments of metals, e.g., in coating base metal parts with an adherent coating of zinc, cadmium or similar protective metal by means of wet impact plating or electroplating, or in chroming or phosphating metal surfaces. A preferred embodiment relates to a wet impact plating process wherein the several solutions used in preparing the work, in plating it and in rinsing it are individually segregated after use and re-used in consecutive plating cycles so that release of ecologically objectionable effluent is eliminated and chemical and metal components fed into the process are conserved instead of being discarded after each plating cycle.
U.S. Pat. No. 4,147,269 discloses a fuel oil storage tank which is a cylindrical vessel of large size and integral molded construction is provided having a depressed well which accumulates sludge formed in the course of storage of hydrocarbon fuels. A hole positioned in the top of the vessel directly above said well permits insertion of a pipe which, by suction means, positioned below the tank and adjacent each end, causes the entire vessel to be tilted downwardly toward the well, thereby causing gravimetric migration of sludge toward the well.